Positive metal image-forming element and process

ABSTRACT

This invention relates to photographic processes for the formation of positive, metal, nonsilver halide photographic images and to photographic elements for carrying out these processes. A photographic element having a metal, e.g., silver, surface or a surface having thereon nonsilver halide nuclei, e.g., silver particles, and a photoreactive composition comprising a spectral sensitizing dye, a mercaptan and an Alpha , Beta unsaturated monomer, adsorbed to said surface or nuclei which inhibits the removal of said metal or nuclei by chemical solvents or bleaching agents is featured in the present process. Upon imagewise exposure of said element to light, the inhibiting effect of the photoreactive composition is destroyed; and subsequent treatment with a bleaching agent removes the exposed metal surface or nonsilver halide nuclei, resulting in the formation of a direct positive metal photographic image or an active site capable of physical development to a negative metal photographic image.

United States Patent Gilman, Jr.

[54] POSITIVE METAL IMAGE-FORMING ELEMENT AND PROCESS [72] Inventor: Paul B. Gilman, Jl., Rochester, N.Y.

[73] Assignee: Eastman Kodak Company, Rochester,

[22] Filed: June 18, 1969 [21] Appl. No.: 834,533

[52] U.S. Cl. ..96/36, 96/36.3, 96/36.4,

96/48 PD, 96/86, 96/88, 96/64 [51] Int. Cl ,.G03c 5/00 [58] Field of Search ..96/27, 64, 86, 88, 36, 48 PD [56] References Cited UNITED STATES PATENTS 3,377,169 4/1968 Blake ..96/88 3,404,980 10/1968 Gilman et al. ..96/27 Mar. 14, 1972 ABSTRACT This invention relates to photographic processes for the formation of positive, metal, nonsilver halide photographic images and to photographic elements for carrying out these processes. A photographic element having a metal, e.g., silver, surface or a surface having thereon nonsilver halide nuclei, e.g., silver particles, and a photoreactive composition comprising a spectral sensitizing dye, a mercaptan and an a, B unsaturated monomer, adsorbed to said surface or nuclei which inhibits the removal of said metal or nuclei by chemical solvents or bleaching agents is featured in the present process. Upon imagewise exposure of said element to light, the inhibiting effect of the photoreactive composition is destroyed; and subsequent treatment with a bleaching agent removes the exposed metal surface or nonsilver halide nuclei, resulting in the formation of a direct positive metal photographic image or an active site capable of physical development to a negative metal photographic image.

FIELD OF THE INVENTION This invention relates to photography, to a process for forming metal, nonsilver halide photographic images and to an element for forming metal images.

In one aspect, this invention relates to use of a photoreactive composition to form direct positive metal silver images of light-insensitive silver particles. In another aspect it relates to use of a photoreactive composition to form negative latent images of nonsilver halide nuclei capable of physical development to a visible silver or other metal image. In still another aspect, it relates to a photographic element having a metal surface and having adsorbed to the metal surface a photoreactive composition which inhibits bleaching of the metal surface.

DESCRIPTION OF THE PRIOR ART In the main, known photographic processes are based on the use of silver halide emulsion coatings. In these processes a latent image is formed by imagewise exposure of a light-sensitive silver halide emulsion layer. In such processes, silver halide bearing a latent image has been developed to silver by selective reduction while the unreduced silver remaining after development has been removed by silver halide solvents including materials capable of chemically rendering the unreduced silver insensitive or transparent. Optional further treatments include intensification, reduction, toning and tinting. However, the primary or first step in image formation in this type of process always has been based on a selective reduction step and restricted to a silver halide material.

Another recently developed type of photographic process is characterized by a specially prepared silver halide emulsion layer containing a stipulated amount of an organic compound which modifies the silver halide solubility so that, in conventional silver halide solvents, the organic compound causes the silver halide grains to dissolve more slowly than normal. An element containing such an emulsion layer is given an imagewise exposure and the exposed areas can then be treated in a solution of a silver halide solvent to yield a positive silver halide image.

SUMMARY OF THE INVENTION In the present invention, an entirely different type of photographic element is provided and a process for using this element for the formation of positive metal images is provided. The element of the present invention comprises a photographic element comprising a support having thereon a metal surface or a surface having thereon nonsilver halide particles, and a photoreactive composition adsorbed to the metal surface or particles which inhibits both chemical reactivity of the metal with a chemical bleaching agent for said metal and physical development of the metal until exposure to actinic radiation destroys said inhibiting effects of said photoreactive composition. The process of the present invention comprises (a) exposing, imagewise, to actinic radiation the photographic element of this invention and (b) contacting said photographic element with a chemical bleaching agent for said metal, thereby effecting removal, in an imagewise manner, of the metal, nonsilver halide material exposed to actinic radiation.

At the outset, a primary advantage of the present invention is readily apparent; namely, the fact that the present invention does not involve a silver halide material. In fact, a primary object of the present invention is to provide a product and a process for forming positive metal images from substances other than silver halides. Accordingly, the present invention is clearly divorced from the prior art processes of image formation which primarily depend either upon a first step based on selective reduction or utilize a photographic element requiring a silver halide material.

Other objects and advantages will become apparent from the following description.

DESCRIPTION OF THE PREFERRED EMBODIMENTS It is preferred that the photoreactive composition comprise a photoreactive sulfur compound which inhibits chemical removal, in an imagewise manner, of the metal surface or the non-silver halide particles on the imagewise exposed photographic element, an a, B-unsaturated compound and a spectral sensitizing dye which induces photoreactivity of said sulfur compound in the visible region of the spectrum. Although the photoreactive sulfur compound together with an afi-unsaturated compound may be used alone as the photoreactive composition, it is preferred to use the spectral sensitizing dye in combination with said photoreactive sulfur compound and a,B-unsaturated compound because generally photoreactive sulfur compounds are photo activated only after long exposure to ultraviolet light, whereas the addition of a spectral sensitizing dye, such as Rose Bengal will extend the region of spectral sensitization of the photoreactive composition to longer wave lengths including the visible region. Moreover, addition of a spectral sensitizing dye also increases the speed of the overall process.

According to a preferred aspect of the invention, the nonsilver halide particles utilized in the present process are silver nuclei. Utilization of silver particles results in an especially preferred embodiment of the present invention in that a direct positive silver image can thereby be obtained.

According to another embodiment of the present invention non-silver halide particles, following aforesaid step of contacting the photographic element with a chemical bleaching agent, are utilized as active sites for physical development by subjecting the photographic element to additional steps which comprise (c) exposing said element to actinic radiation to destroy the inhibiting effect of the photoreactive composition adsorbed on the remaining nuclei previously unexposed to actinic radiation and (d) contacting said element with a solution of a metallic compound, thereby effecting physical development of a negative metallic image.

In the practice of the present invention the photoreactive composition which is adsorbed to .a metallic surface or to metallic non-silver halide particles may be applied by contacting the photographic element comprising a support having metal thereon with the photoreactive composition, such as by bathing the support having coated thereon metallic nonsilver halide particles in a solution of the photoreactive composition. Or, the photoreactive composition may be incorporated directly into a coating for the support wherein said coating contains both metallic, non-silver halide particles and the photoreactive composition. Preferably, a nonpolymeric photoreactive composition is used.

With respect to the materials utilized to form the abovedescribed photoreactive composition, a broad class of thiophenol compounds are preferred. Especially preferred are those compounds having at least one form which can be represented by the general formula R-SH where R is an organic radical having a carbon atom linked directly to S. These compounds include the heterocyclic mercaptans, the dimercaptans, the aromatic mercaptans, the aliphatic mercaptans, and the like. Mixtures of two or more may be used. The heterocyclic mercaptans can be selected from, although they are not limited to, compounds selected from the class comprising:

2-mercapto-4-phenylthiazole Z-mercaptobenzothiazole 6-amiro-2-mercaptobenzothiazole 6-nitro-Z-mercaptobenzothiazole l-phenyl-5-mercaptotetrazole -thiohydantoin 5-(2-hydroxybenzylidene)-2-thiohydantion 2-mercaptobenzimidazole 2-mercapto-S-aminobenzimidazole 2-mercapto-5-nitrobenzimidazole 2-mercaptobenzoxazole Z-mercapto quinoline 2-naphtho( l ,2 )-thiazolethiol Phenyl biquanide mercapto benzothiazole 2-mercapto-5,-dimethoxybenzothiazole 6-acetylamino-2-mercapto benzothiazole G-isobutylrylamino-Z-mercaptobenzothiazole 6-n-octanoylamino-2-mercaptobenzothiazole 6-lauroylamino-2-mercaptobenzothiazole 4-phenyl-l ,3,4-thiadiazolidene-2-thione 5,6-dihydro-4-phenyl-4H-l ,3,4-thiadiazine-2-thio The dimercaptans can be selected from, although they are not limited to, compounds selected from the class comprising:

2,3-quinoxalinedithiol 2,3-dimercaptopropanol Toluene-3,4-dithiol Glycol dimercapto acetate Cyclohexane-l ,1-dithiol 2 ,5 -dimercaptol ,3,4-thiadiazole 5,S-thiobis-( 1,3, 4-thiadiazole 2-thiol) 3,5-dimercapto-4-cyanol ,2-thiazole N-cyano imine dipotassium dithiolate l ,1-dicyano-2,2-disodium dithiolate ethylene 2-cyano-3,3 disodium dithiolate acrylamide 2-cyano-3,3-dipotassium dithiolate ethyl acrylate C is-dicyanoethylene disodium thiolate Trans-dicyano dithiolate ethylene ditetramethylammonium salt 3 ,5 -disodium dithiolate-4-cyano-l ,2-thiazole The aromatic mercaptans can be selected from, although they are not limited to, compounds selected from the class comprising:

Thiophenol B-Naphthothiol p-Chlorothiophenol 2-aminothiophenol 4-aminothiophenol p-Bromothiophenol p-Nitrothiophenol Thiosalicylic acid O-Toluenethiol m-Toluenethiol p-Toluenethiol 4-t-butylthiophenol 4-n onylthiophenol 4-t-butyl-o-thiocresol The aliphatic mercaptans can be selected from, although they not limited to, compounds selected from the class comprising: N-Propyl mercaptan lospropyl mercaptan n-Butyl mercaptan lsobutyl mercaptan Sec. butyl mercaptan t-Butyl mercaptan n-Amyl mercaptan 2-pentanethiol Sec. amyl mercaptan t-Amyl mercaptan n-Hexyl mercaptan n-Heplyl mercaptan n-Octyl mercaptan t-Octyl mercaptan Z-ethyll -hexanethiol n-Nonyl mercaptan n-Decyl mercaptan n-Undecyl mercaptan n-Dodecyl mercaptan t-Dodecyl mercaptan Benzyl mercaptan O-Methyl benzyl mercaptan p-Methyl benzyl mercaptan O-Ethyl benzyl mercaptan p-Ethyl benzyl mercaptan p-Methoxybenzyl mercaptan Additional compounds include 7, lB-dithianonadecane-l, l9- bispyridinium-p-toluenesulfonate, 3-n1ercapto-l,2,4-triazole, l -octyll ,2,3,6-tetrahydro-l ,3 ,5-triazine-4-thiol, l-decyll ,2,3,6-tetrahydrol ,3,5,-triazine-4-thiol, 1-hexyl-l,2,3,6- tetrahydro-1,3,5-triazine-4-thiol, l-propyll ,2,3,6-tetrahydrol-ethyl-l,2,3,6tetrahydro-1,3,5- triazine-4-thiol, l-cyclohexyll ,2,3 ,o-tetrahydro-l ,3 .5 triazine-4-thiol, l-mono-sec-butyll ,2,3,6-tetrahydro- 1,3,5- triazine-4thiol, piperindinylmethyl-Z-thio-oxazolidine, 2-mercaptobenzimidazole, 3,9-dithiaundecanel l l-bis-( N-methylmorpholinium )-p-tolunen mercapto-S-methyl-1,2,4-triazole, 2-benzoxazole-thiol, l-( 3-aminophenyl)-5-mercapto-tetrazole hydrochloride l-( 3-methylsulfonamidophenyl)-5-mercaptotetrazole, l-(4-caproylaminophenyl )-5-mercaptotetrazole.

In a preferred embodiment of the present invention wherein the photoreactive composition comprises an aB-unsaturated compound and a spectral sensitizing dye in addition to a photoreactive sulfur compound, the following materials are illustrative of suitable afi-unsaturated compounds and spectral sensitizing dyes. a,B-unsaturated indicates unsaturation between carbons adjacent to a carbon atom substituted by an active group. Typical examples of the afi-unsaturated compounds which serve as acceptors for the photoreactive sulfur compound are compounds selected from the class comprising:

Cellosolve acrylate Dimethylaminoethyl methacrylate Phenyl butynol 2,3-dibromo-2-butentl ,4 -diol Z-butene-l-ol 10% in water) 3-butenenitride 2-propyne-l-ol 10% in water) 2-methyl-3-butyne-2-ol (10% in water) Ethylene dicyclohexanol 2,3-butynel ,4 -diol Acrylamide Typical examples of the spectral sensitizing dyes are materials selected from the class comprising Rose Bengal, Eosin blue, Eosin yellow, tetraiodofluorescein, methylene blue; the pyrylium dye, 2,6-Bis(4-ethylphenyl)-4-(4-n-amyloxyphenyl)- thiopyrylium perchlorate and the like. It will be recognized of course that, in part, the choice of a particular sensitizing dye and a particular a, B-unsaturated compound will depend upon the particular photoreactive sulfur compound utilized in the preparation of the photoreactive composition.

The nonsilver halide materials which can be used in the practice of the present invention include a wide variety of substances. For example, the noble metals and those metals which are members of the electromotive scale below hydrogen are typically employed in the practice of the present invention. These metals include, for example, such substances as copper, arsenic, antimony, mercury, platinum, gold, silver and the like. Other substances which are utilized as nonsilver halide nuclei in the process of the present invention are, for example, the sulfides and selenides. Examples of these substances are lead sulfide and selenide, zinc sulfide and selenide, nickel sulfide and selenide, and the like. In addition, substances such as zinc oxide, zinc hydroxide, and lead iodide have also been found to serve as suitable nonsilver halide materials. it should also be noted that the nonsilver halide materials useful in the practice of the present invention include both light-insensitive and light-sensitive materials, for example, silver is light insensitive, while lead iodide is a light-sensitive material.

In some embodiments, the materials are particles having an average diameter as small as 25 A. A particularly useful range of particle sizes is from about 25 A. to about 100,000 A. One more materials may be used in the coating.

The surface on the support can be a continuous metal layer of one or more of the metal materials useful in the practice of this invention. in fact, the metal layer can be self supporting, e.g., a sheet of copper, aluminum or the like. A particularly useful element for lithographic printing comprises a thin uniform coating of metal material on a surface which has a different ink-water affinity than that of the metal material. For instance, a coating of aluminum can be deposited on a copper plate by a convenient method, such as vacuum deposition, and by using this invention, be etched to provide a useful lithographic printing plate. Particularly useful metal layers have a thickness of 0.01 to 1.0 mil.

1 ,3,5-triazine-4-thiol,

In another embodiment, a stencil can be provided by coating a thin layer of metal on a porous support, such as teabag stock or the like. The solubilizing action is restrained by the inhibiting agent in those areas where the inhibiting agent has not be exposed to light.

With respect to the chemical bleaching agents utilized in the practice of the present invention, it will again be recognized that a wide variety of various chemical bleaching agents, including solvents for the metal materials and other chemicals capable of chemically removing and/or rendering the unexposed nuclei transparent can be used. Accordingly, the practice of the present invention is certainly not restricted to silver halide solvents and chemical bleaches for silver. The essential feature characterizing the chemical agent utilized is simply that the particular chemical agent chosen must be capable of removing or rendering transparent the particular non-silver halide material utilized. Accordingly, the choice of a particular bleaching agent will depend on the particular nonsilver halide utilized. An example of a preferred chemical bleaching agent which may be utilized when silver is employed as the metal nonsilver halide material is a ferricyanide bleach bath. Such a bleach bath has been published in the Kodacolor Manual, October, I955, Chemistry of Mixing Formulas, page I of I, No. 2623. In general, since a large number of chemical bleaching agents are well known in the photographic art, numerous other types and varieties of chemical bleaching agents which can be utilized in the practice of the present invention will be obvious to those of ordinary skill in the art. These include permanganate, persulfate, ferricyanate, etc.

In preparing the photographic elements used in the process of the present invention, supporting materials, if desired, can be any of the known materials for this purpose, such as film base (e.g., cellulose nitrate film, cellulose ester film, etc.), plastic supports (e.g., polyethylene, polyethylene terephthalate, etc.) paper, metal, glass, and the like.

Suitable binders for incorporating the present nonsilver halide particles can include any of the water-permeable materials, such as gelatin or other hydrophilic materials, such as collodion, albumin, cellulose derivatives, certain synthetic resins, polyvinyl alcohol, and the like.

The present invention will be further illustrated by it, but it is not to be limited to, the following examples:

EXAMPLE I A strip of uniformly exposed photographic film is developed by conventional means to produce a metal silver image, Dmax=l.5. This developed photographic element is then immersed, under safelight conditions, in a solution containing 3 ml. of a 1 percent methanolic solution of phenyl mercaptotetrazole a photoreactive compound which is a heterocyclic mercaptan), 9 ml. of a 50 percent ethanol-water solution of acrylamide (90 parts ethanol, 10 parts water), and 2 ml. ofa 1 percent aqueous solution of the spectral sensitizing dye Rose Bengal. After the processed element is immersed in the above solution for 30 seconds, it is dried and exposed imagewise for 10 seconds to a photoflood lamp at a distance of l8-inches. The photographic element is then immersed in a ferricyanide bleach bath for 30 seconds.

As a result of the above process, it is found that in the imagewise exposed areas the photoreactive sulfur compound is removed; preferential bleaching of the imagewise exposed silver nuclei is obtained; and in the unexposed areas where the photoreactive sulfur compound is still tightly adsorbed to the silver nuclei surface, the action of the chemical bleaching agent on the silver nuclei is effectively inhibited, thereby yielding a good direct, positive silver image.

Similar results are obtained when the spectral sensitizing dyes Eosin blue, Eosin yellow, tetraiodofluorescein, methylene blue and the pyrylium dye, 2,6-bis(4-ethylphenyl)- 4-(4-n-amyloxyphenyl)-thiapyrylium perchlorate, are substituted for the sensitizing dye, Rose Bengal.

EXAMPLE 2 In this example, a process identical to Example 1 above is utilized except the image-forming material is a sheet of 0.001

inch copper foil. The foil is sensitized by dipping in the sensitizing solution described in Example 1. After imagewise exposure and bleaching in an aqueous solution, containing 50 g./l. potassium ferricyanide preferential etching of the copper sheet takes place in the exposed areas.

EXAMPLE 3 In this example a process identical to Example 1 above is utilized except that a dimercaptan, 2,3-dimercaptopropanol, is substituted for the photoreactive sulfur compound utilized in Example 1. And again, a satisfactory direct positive silver image is obtained.

EXAMPLE 4 Here again a process identical to that illustrated in Example 1 is utilized except that an aromatic mercaptan, thiophenol, is substituted for the photoreactive sulfur compound utilized in Example I. And again a satisfactory direct positive metal silver image is obtained.

EXAMPLE 5 A process identical to Example 1 is utilized except that an aliphatic mercaptan, n-butyl mercaptan, is employed as the photoreactive sulfur compound. And again a satisfactory direct positive silver image is obtained.

EXAMPLE 6 In this example the photographic element is a strip of photographic film having thereon nuclei of silver metal. However, in this example, the photoreactive composition contains only the photoreactive sulfur compound, phenylmercaptotetrazole, and the a,fl-unsaturated compound, acrylamide. That is, the photographic element is immersed, under safelight conditions, in a solution containing 3 ml. of a 1 percent methanolic solution of phenylmercaptotetrazole and 9 ml. of a 50 percent ethanol-water solution of acrylamide. After the silver containing strip is immersed in the above solution for 30 seconds, it is dried and exposed imagewise for one-half hour to an ultraviolet light at a distance of 18 inches. The photographic element is then immersed in a ferricyanide bleach bath for 30 seconds. And again, as in the above examples a satisfactory direct positive metal silver image is obtained. However, it will be noted in this example that since the spectral sensitizing dye is not utilized, long exposure to ultraviolet light is needed to cause photoreaction of the photoreactive sulfur compound.

EXAMPLE 7 In this example a strip of film support having thereon colloidal copper nuclei is utilized. The mean size of the colloidal copper employed is roughly 1,000 A. This film has a uniform density about 0.1. This photographic element is then immersed, under safe-light conditions, in a solution identical to that utilized in Example 1. After the element is immersed in the solution for 30 seconds, it is dried and is given an imagewise exposure for 10 seconds to a photoflood lamp at a distance of 18 inches. The strip is then immersed in a chemical bleaching agent for copper nuclei, i.e., ferricyanide, for 30 seconds. In the imagewise exposed areas, the photoreactive sulfur compound is removed; preferential bleaching of the imagewise exposed copper nuclei is obtained; and in the unexposed areas where the photoreactive sulfur compound is still tightly adsorbed to the copper nuclei surface, the action of the bleaching agent on the copper nuclei is effectively inhibited.

As a result of the above treatment, the copper nuclei in the unexposed areas where the photoreactive sulfur compound is still tightly adsorbed to the surface of the copper nuclei now form a positive latent image and are potentially active sites for physical development. Accordingly, the strip of photographic film is exposed to a photoflood lamp at a distance of 18 inches for a period of 10 seconds in order to destroy the inhibiting effect of the photoreactive sulfur composition adsorbed on these remaining copper nuclei previously unexposed to actinic radiation. As a final step, the strip of photographic film is then physically developed by contacting the strip of film with an aqueous silver solution of dilute silver nitrate solution, immersing the film in a developing solution containing hydroquinone, followed by washing the developed film with water to stabilize it, thereby resulting in a silver image in the originally unexposed areas. Similar results are obtained when the copper nuclei are replaced by silver are palladium nuclei EXAMPLE 8 In this example a process identical to that utilized in Example 7 above is employed except that light sensitive lead iodide nuclei are substituted for the copper nuclei. And, once again, after physically developing the strip of photographic film with a solution containing a silver compound, a positive silver image is obtained.

In the above application, our examples have been specific to metal images in which silver is used to form an image. However, other metals can be used for the same purpose as silver by the appropriate substitution. Metals which are members of the electromotive scale below hydrogen, examples of which have been enumerated hereinabove, are those which are most commonly employed for this purpose. The use of these metals to form images is within the scope of this invention. It has not been practical to show an example for each and every one of these metals, but silver images are believed to be those most preferred.

The invention has been described in detail with particular reference to a preferred embodiment thereof, but it will be understood that variations and modifications can be effective within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

I claim:

1. A photographic element comprising a continuous layer of a metal below hydrogen on the electromotive scale having adsorbed to said layer a nonpolymeric sulfur containing photoreactive composition which inhibits bleaching of said layer until exposure light destroys the inhibiting effect of said photoreactive composition.

2. A photographic element of claim 1 in which said layer is on a support.

3. A photographic element of claim 1 in which said photoreactive composition is a mixture of a sulfur compound which inhibits bleaching of said layer, an afiunsaturated compound and a spectral sensitizing dye.

4. A photographic element of claim 1 in which said composition is a mixture of a sulfur compound selected from the class consisting of 7,13-dithianonadecane-l,l9-bis-pyridinium-p-toluenesulfonate, 3-mercapto-l,2,4-triazole, l-octyll ,2,3,6-tetrahydro-1,3,5-triazine-4-thiol, l-decyl-l 2,3,6- tetrahydrol ,3 ,5-triazine-4-thiol, l-hexyl-l ,2,3 ,o-tetrahydrol ,3 ,5-triazine-4-thiol, l-propyll ,2,3,6-tetrahydrol ,3,5,- triazine-4-thiol, l-ethyll ,2,3 ,Gtetrahydro-l ,3,5,-triazine-4- thiol, l-cyclohexyl-l ,2,3,6-tetrahydro-l ,3,5-triazine-4-thiol, l-mono-scc-butyll ,2,3 ,o-tetrahydrol-l ,3 ,5-triazine-4-thiol, piperindinylmethyl-2-thio-oxazolidine, Z-mercaptobenzimidazole, 3,9-dithiaundecane-l ,1 l-bis( N-methylmorpholinium )-p-toluene mercapto-S-methyl-l ,2,4-triazole, Z-benzoxazole-thiol, i-( B-aminophenyl )--mercapto-tetrazole hydrochloride, l-(3-methylsulfonamidophenyl )-5-mercaptotetrazole, l -(4-caproylaminophenyl )-5-mercaptotetrazole and l-(S-acetamidophenyl)-5-mercaptotetraz0le adsorbed on said layer, an afiunsaturated compound and a spectral sensitizing dye.

5. A photographic element of claim 1 in which said composition is a mixture of a sulfur compound which inhibits bleaching of said layer, a spectral sensitizing dye and an a, [3-

unsaturated compound selected from the class consisting of cellulose acrylate, dimethylaminoethyl methacrylate, phenyl butynol, 2,3-dibromo-2-butene-l,4-diol, 2-butene-l-ol, 2-butone-nitride, 2-propyne-l -ol, ethylene dicyclohexanol, 2,3-butyne-1,3-diol and an acrylamide.

6. A photographic element of claim 1 in which said photoreactive composition is a mixture of a sulfur compound which inhibits bleaching of said layer, a spectral sensitizing dye and alpha, beta unsaturated vinyl monomer.

7. A photographic element of claim 3 in which the sensitizing dye is selected from the class consisting of Rose Bengal, Eosin blue, Eosin yellow, tetraiodofluoroescein and meth lene blue. I

8. process for forming a metallic image in a light sensitive layer which comprises (a) exposing, imagewise, to actinic radiation a photographic element comprising a continuous layer of a metal below hydrogen on the electromotive scale having absorbed to said layer a nonpolymeric sulfur containing photoreactive composition which inhibits bleaching of said layer until exposure to actinic radiation destroys said inhibiting effects of said photoreactive composition and (b) contacting said photographic element with a chemical bleaching agent for said material, thereby effecting removal, in an imagewise manner, of said material exposed to actinic radiation.

9. A process for the preparation of a direct positive photographic image according to claim 8 wherein the metal is silver.

10. A process for the preparation of a direct positive photographic image according to claim 9 wherein the photoreactive composition comprises a photoreactive sulfur compound which inhibits chemical removal, in an imagewise manner, of said material on said imagewise exposed photographic element, an a, fl-unsaturated compound and a spectral sensitizing dye which induces photoreactivity of said sulfur compound in the visible region of the spectrum.

11. A process according to claim 10 wherein said spectral sensitizing dye is selected from the class consisting of Rose Bengal, Eosin blue, Eosin yellow, tetraiodofluorescein, and methylene blue.

12. A process according to claim 10 wherein said (I, dunsaturated compound is selected from the class consisting of cellulose acrylate, dimethylaminoethyl methacrylate, phenyl butynol, 2,3-dibromo-2-butenel ,4-diol, 2-butene- 1 -ol( lOpercent water), 3-butenenitride, 2-pr0pyne-lol( 10 percent in water), 2-methyl-3-butyne-2-ol( 10 percent in water), ethylene dicyclohexanol, 2,3-butyne-l,4-diol, and an acryla mide.

13. A process according to claim 10 wherein said photoreactive sulfur compound in at least one form is represented by the formula RSH where R is an organic radical having a carbon atom linked directly to S.

14. A process according to claim 10 wherein said photoreactive sulfur compound is phenyl mercaptotetrazole.

15. A process according to claim 9 wherein the photoreactive composition comprises a photoreactive sulfur compound an an afi-unsaturated compound.

16. A process according to claim 10 wherein said photoreactive sulfur compound is selected from the class consisting of heterocyclic mercaptans, dimercaptans, aromatic mercaptans, and aliphatic mercaptans. 

2. A photographic element of claim 1 in which said layer is on a support.
 3. A photographic element of claim 1 in which said photoreactive composition is a mixture of a sulfur compound which inhibits bleaching of said layer, an Alpha , Beta unsaturated compound and a spectral sensitizing dye.
 4. A photographic element of claim 1 in which said composition is a mixture of a sulfur compound selected from the class consisting of 7,13-dithianonadecane-1,19-bis-pyridinium-p-toluenesulfonate, 3-mercapto-1,2,4-triazole, 1-octyl-1,2,3,6-tetrahydro-1,3,5-triazine-4-thiol, 1-decyl-1,2,3,6-tetrahydro-1, 3,5-triazine-4-thiol, 1-hexyl-1,2,3,6-tetrahydro-1,3,5-triazine-4-thiol, 1-propyl-1,2,3,6-tetrahydro-1,3,5,-triazine-4-thiol, 1-ethyl-1,2,3,6tetrahydro-1,3,5,-triazine-4-thiol, 1-cyclohexyl-1, 2,3,6-tetrahydro-1,3,5-triazine-4-thiol, 1-mono-sec-butyl-1,2,3, 6-tetrahydrol-1,3,5-triazine-4-thiol, piperindinylmethyl-2-thio-oxazolidine, 2-mercaptobenzimidazole, 3,9-dithiaundecane-1,11-bis(N-methyl-morpholinium)-p-toluene mercapto-5-methyl-1,2,4-triazole, 2-benzoxazole-thiol, 1-(3-aminophenyl)-5-mercapto-tetrazole hydrochloride, 1-(3-methylsulfonamidophenyl)-5-mercaptotetrazole,1-(4-caproylaminophenyl)-5-mercaptotetrazole and 1-(3-acetamidophenyl)-5-mercaptotetrazole adsorbed on said layer, an Alpha , Beta unsaturated compound and a spectral sensitizing dye.
 5. A photographic element of claim 1 in which said composition is a mixture of a sulfur compound which inhibits bleaching of said layer, a spectral sensitizing dye and an Alpha , Beta -unsaturated compound selected from the class consisting of cellulose acrylate, dimethylaminoethyl methacrylate, phenyl butynol, 2,3-dibromo-2-butene-1,4-diol, 2-butene-1-ol, 2-butene-nitride, 2-propyne-1-ol, ethylene dicyclohexanol, 2,3-butyne-1,3-diol and an acrylamide.
 6. A photographic element of claim 1 in which said photoreactive composition is a mixture of a sulfur compound which inhibits bleaching of said layer, a spectral sensitizing dye and alpha, beta unsaturated vinyl monomer.
 7. A photographic element of claim 3 in which the sensitizing dye is selected from the class consisting of Rose Bengal, Eosin blue, Eosin yellow, tetraiodofluoroescein and methylene blue.
 8. A process for forming a metallic image in a light sensitive layer which comprises (a) exposing, imagewise, to actinic radiation a photographic element comprising a continuous layer of a metal below hydrogen on the electromotive scale having absorbed to said layer a nonpolymeric sulfur containing photoreactive composition which inhibits bleaching of said layer until exposure to actinic radiation destroys said inhibiting effects of said photoreactive composition and (b) contacting said photographic element with a chemical bleaching agent for said material, thereby effecting removal, in an imagewise manner, of said material exposed to actinic radiation.
 9. A process for the preparation of a direct positive photographic image according to claim 8 wherein the metal is silver.
 10. A process for the preparation of a direct positive photographic image according to claim 9 wherein the photoreactive composition comprises a photoreactive sulfur compound which inhibits chemical removal, in an imagewise manner, of said material on said imagewise exposed photographic element, an Alpha , Beta -unsaturated compound and a spectral sensitizing dye which induces photoreactivity of said sulfur compound in the visible region of the spectrum.
 11. A process according to claim 10 wherein said spectral sensitizing dye is selected from the class consisting of Rose Bengal, Eosin blue, Eosin yellow, tetraiodofluorescein, and methylene blue.
 12. A process according to claim 10 wherein said Alpha , Beta -unsaturated compound is selected from the class consisting of cellulose acrylate, dimethylaminoethyl methacrylate, phenyl butynol, 2,3-dibromo-2-butene-1,4-diol, 2-butene-1-ol(10percent water), 3-butenenitride, 2-propyne-1ol(10 percent in water), 2-methyl-3-butyne-2-ol(10 percent in water), ethylene dicyclohexanol, 2,3-butyne-1,4-diol, and an acrylamide.
 13. A process according to claim 10 wherein said photoreactive sulfur compound in at least one form is represented by the formula R-S-H where R is an orgaNic radical having a carbon atom linked directly to S.
 14. A process according to claim 10 wherein said photoreactive sulfur compound is phenyl mercaptotetrazole.
 15. A process according to claim 9 wherein the photoreactive composition comprises a photoreactive sulfur compound an an Alpha , Beta -unsaturated compound.
 16. A process according to claim 10 wherein said photoreactive sulfur compound is selected from the class consisting of heterocyclic mercaptans, dimercaptans, aromatic mercaptans, and aliphatic mercaptans. 